Selective crystallization represents one of the most economical and convenient methods to provide large-scale optically pure chiral compounds. Although significant development has been achieved since Pasteur’s separation of sodium ammonium tartrate in 1848, this method is still fundamentally low efficient (low transformation ratio or high labor). Herein, we describe an enantiomer-selective-magnetization strategy for quantitatively separating the crystals of conglomerates by using a kind of magnetic nano-splitters. These nano-splitters would be selectively wrapped into the S -crystals, leading to the formation of the crystals with different physical properties from that of R -crystals. As a result of efficient separation under magnetic field, high purity chiral compounds (99.2 ee% for R -crystals, 95.0 ee% for S -crystals) can be obtained in a simple one-step crystallization process with a high separation yield (95.1%). Moreover, the nano-splitters show expandability and excellent recyclability. We foresee their great potential in developing chiral separation methods used on different scales.

Collection of two optically pure enantiomers in a single crystallization process can significantly increase the chiral separation efficiency but this is difficult to realize. Now a self-reporting strategy is presented for visualizing the crystallization process by a dyed self-assembled inhibitor made from the copolymers with tri(ethylene glycol)-grafting polymethylsiloxane as the main chain and poly(N -methacryloyl-l-lysine) as side chains. When applied with seeds together for the fractional crystallization of conglomerates, the inhibitors can label the formation of the secondary crystals and guide the complete separation process of two enantiomers with colorless crystals as the first product and red crystals as the second. This method leads to high optical purity of d/l-Asn⋅H O (99.9 % ee for d-crystals and 99.5 % for l-crystals) in a single crystallization process. It requires a small amount of additives and shows excellent recyclability.

Collecting both enantiomorphs with high optical purity and yield in a single crystallization process can be achieved by adding aggregated polymeric “tailor‐made” additives, known as nano‐splitters. Inefficient preparation and large addition amount have hindered the practical application of such amazing nanoparticles. Herein, we report the first nano‐splitters containing aggregation‐induced emission luminogens prepared via polymerization‐induced self‐assembly of block copolymer, poly[(S)‐2‐(tert‐butoxycarbonylamino)‐6‐(methacrylamido)hexanoic acid]‐b‐polystyrene, followed by the removal of tert‐butoxycarbonyl groups. When added into the supersaturated solution of racemic amino acids (a.a.) with seeds, the fluorescent labeled nano‐assemblies enantioselectivity dyed the crystals of S‐a.a. and enabled the separation from colorless R‐a.a. crystals in terms of fluorescent difference. Both enantiomers were obtained with high optical purity and yield (e.g., R‐ asparagine monohydrate, >99 ee%; S‐ asparagine monohydrate, ∼94 ee%; 88% total yield). Owing to a low detection limit of fluorescence, the addition amount was reduced to 0.03 wt% without remarkably compromising the ee values of both enantiomorphs. Due to the low addition amount and efficient synthesis, the output–input ratio was increased greatly.